Determine whether Dzyaloshinskii–Moriya interaction causes asymmetric 2D criticality

Determine whether the Dzyaloshinskii–Moriya interaction causes the distinct critical behaviors observed below and above the magnetic transition temperature in the quasi-two-dimensional non-centrosymmetric hybrid perovskite (C₇H₉NBr)₂CuBr₄.

Background

The paper reports asymmetric critical exponents in the DMI-active quasi-two-dimensional compound (C₇H₉NBr)₂CuBr₄: 2D Ising-type criticality is observed below the transition temperature, whereas 2D XY-type criticality is observed above it. Isostructural and centrosymmetric analogues with weaker expected DMI exhibit conventional, approximately symmetric 2D critical behavior.

The authors attribute the asymmetry to DMI influencing critical fluctuations and correlations differently on the two sides of the transition, but they present this attribution as a conjecture rather than as an established causal explanation. Consequently, the microscopic role of DMI remains to be tested, particularly through theoretical and numerical studies of quasi-2D magnets and controlled 2D simulations.